1. Field of the Invention
The present invention is directed to a reformer which is associated with a fuel cell system.
2. Description of the Related Art
Generally speaking, in fuel cell systems, electric power is generated in a fuel cell stack by using a fuel gas and an oxidizing agent gas. The fuel gas is supplied from a reformer in which a fuel of the hydrocarbon family is reformed into a fuel gas whose principal component is hydrogen. Due to the fact that such a fuel gas involves 0.3-2% CO, it can cause poisoning of the electrode catalyst, thereby considerably lowering the performance of the fuel cell system.
To prevent such a drawback, Japanese Laid-open Patent No. Hei.8-100184, published in 1996 without examination, discloses a carbon monoxide removing system in which a raw material to be reformed is first used for cooling the carbon monoxide removing system and thereafter is reformed so as to reduce the CO concentration in a hydrogen-rich fuel gas below 100 ppm.
However, if a load of the fuel call system increases, the flow mass of the raw material also increases, which causes an abrupt cooling of the carbon monoxide removing system, thereby unbalancing the same in temperature. Due to the fact that the operation of a reformer is based on the temperature of the carbon monoxide removing system, such an imbalanced condition may cause an unexpected operation of the reformer.
It is therefore a principal object of the present invention to provide a reformer which is free from the foregoing drawback.
In order to attain the above and other objects, the present invention provides a reformer, especially for fuel cell systems, which comprises an evaporation portion for evaporating a hydrocarbon family fuel and a water as raw materials; a reforming portion for producing a reformed gas whose principal element is hydrogen from the raw materials; a CO-reduction portion for reducing CO involved in the reformed gas; a circulating conduit portion including storage means for storing one of the hydrocarbon family fuel, the water, and a mixture of the hydrocarbon family fuel and the water, a feeding means for feeding one of the raw materials under pressure, and cooling means for cooling the CO reduction portion; and supply means for supplying the raw materials to the evaporation portion, the supply means including a conduit branched from the circulating conduit portion connected to the evaporation portion, and a flow control means provided in the conduit.